Os Draconis-Derived Nanoparticles Improve Insomnia Symptoms by Activating Calcium-Dependent 5-HT Release and the Vagal-NTS Pathway.

Abstract

<h4>Background</h4>Os draconis (OD), a traditional Chinese medicine from fossil mammalian bones, effectively treats insomnia and anxiety. Its usage conflicts with the laws, causing a shortage. This research clarifies OD's pharmacodynamic mechanisms, aiming to establish a scientific basis for developing novel artificial substitutes.<h4>Methods</h4>This research used a mouse chronic insomnia paradigm to assess an os draconis decoction (DOD). DOD was digested in vitro, and the resultant nanoparticles (OD-NPs) were analyzed by scanning electron microscopy, dynamic light scattering, X-ray diffraction, and Fourier transform infrared spectroscopy. The in vivo effects were evaluated using behavioral tests, Nissl staining, neuronal activity in the nucleus tractus solitarii (NTS), and plasma 5-HT levels. In vitro mechanistic investigations used FITC-labeled OD-NPs to detect cellular uptake. The research used calcium channel blockers to examine changes in intracellular Ca²⁺ concentration and critical protein expression in 5-HT-related pathways.<h4>Results</h4>After DOD treatment, significantly improved movement in the Open field, brain malondialdehyde (MDA) and plasma tumor necrosis factor-α (TNF-α) were reduced, increased hippocampal Nissl bodies, and alleviated neuronal damage. Digested DOD formed numerous sub-1000 nm spindle particles. Its composition remained carbonate hydroxyapatite (F-rich), but crystallinity decreased. DOD elevated plasma 5-HT and c-fos expression in the NTS. In vitro, OD-NPs were uptaken by cells, increasing supernatant 5-HT and cytosolic calcium. This upregulated TPH1 and DdC expression, a trend unaffected by Ca²⁺ channel blockade, unlike the filtrate group.<h4>Conclusion</h4>This is the first research to suggest that oral DOD is digested into OD-NPs, which are then internalized by enterochromaffin cells. This absorption initiates calcium signaling, boosts 5-HT release, and then activates the vagus nerve-NTS pathway, thereby regulating central nervous system activity. This research provides scientific proof for the clinical application of OD, lays the groundwork for the development of artificial alternatives, and generates ideas for future traditional Chinese medicine research.